The pibgorn is very diatonic, usually in D, with the occaisional accidental manageable with careful half-holing or cross-fingering. It just plays a straight D major scale by opening each hole in turn, like a whistle, but with a thumb-hole for the top D. That's it, no second octave or overblowing. Some instruments have an extra low C (or C#) under the little finger of the right hand.

Hope this helps

_________________"I'm playing all the right notes—but not necessarily in the right order."